1. Field of the Invention
The present invention relates to a conditioner for a CMP (Chemical Mechanical Polishing) pad, which is used in a CMP process which is part of the fabrication of a semiconductor device, and more particularly, to a CMP pad conditioner in which the structure of the cutting tips is such that the change in the wear of the polishing pad is not great even when different kinds of slurry are used and when there are changes in pressure of the conditioner, and to a method of manufacturing the same.
2. Description of the Related Art
CMP techniques which are useful in semiconductor apparatuses are used to planarize a thin film such as an insulating layer or a metal layer formed on a semiconductor wafer.
A planarization process using CMP is carried out in such a way that a polishing pad is attached onto a platen which rotates and a wafer which is to be polished is held by means of a carrier, and while a slurry is supplied onto the pad, the platen and the carrier are subjected to motion relative to each other in a state of applying pressure to the carrier that holds the wafer, thus polishing the wafer.
In the CMP process for planarization, the uniformity of the removal rate (i.e. polishing uniformity) across the surface of a workpiece such as a wafer is regarded as important. Among a variety of factors for increasing the polishing uniformity, the surface state of the polishing pad may be included as an important quantitative factor.
The preferred surface state of the polishing pad may be achieved by conditioning the polishing pad, including cutting the surface of the deformed pad using a conditioner, in order to restore the worn or clogged pores of the polishing pad and the decreased flatness of the polishing pad to its original state.
As such, the conditioning process enables the surface state of the polishing pad to be optimized to an initial state which has a high ability to retain the slurry, using a pad conditioner having a grinder such as diamond which is put in contact with the polishing pad to scrape or rub the surface of the polishing pad. Alternatively, this process may function to restore the ability of the polishing pad to retain the slurry so that the polishing capability of the polishing pad can be maintained.
Meanwhile, examples of a slurry used in the CMP process may include an oxide slurry, a tungsten (W) slurry, and a copper (Cu) slurry. These slurries may differently affect the pad in the CMP process because they are different in terms of the kind, shape and size of polishing particles and the kind and amount of additives. Also, the case where the material of the pad and the pressure which is applied to the CMP pad conditioner put in contact with the pad are varied may result in having different effects on the pad used in the CMP process.
Thus even when the same CMP pad conditioner is used, the wear of the pad may vary depending on the kind of slurry, the material of the pad and changes in pressure. Upon conditioning, because the conditioner used should be adapted for a slurry, a pad and changes in pressure, numerous products having a variety of specifications should be evaluated to deduce the appropriate CMP pad conditioner, which is considered troublesome.
Particularly among conventional CMP pad conditioners, a diamond electroplating type pad conditioner has the following problems. Specifically, diamond particles for polishing may have a variety of shapes, including a cube shape, an octahedral shape, a cube-octahedral shape, etc. upon preparation, and even when diamond having a predetermined shape is used, it is attached regardless of orientation, making it difficult to control the height of diamond which protrudes, and thereby the area of diamond which is put in contact with the pad cannot be equivalently controlled and thus it is difficult to calculate the area of the diamond put in contact with the pad. This means that the pressure which is applied to respective diamond particles which are put in contact with the pad in the conditioner cannot be predicted, thus making it difficult to predict conditioning performance.
Also Korean Patent No. 10-0387954 discloses a CVD pad conditioner, which comprises a substrate having a plurality of truncated polypyramids protruding upwards at a uniform height from the surface thereof and a diamond layer deposited thereon using CVD. The CVD pad conditioner thus formed may be used under predetermined pressure, but for all that the conditioning of the polishing pad is not performed well in a state of PWR (Pad Wear Rate) being unstable, the extent of increase or decrease in PWR is undesirably very large depending on changes in pressure upon conditioning. Accordingly the conventional CVD conditioner disclosed in the above patent is problematic because the extent of change in PWR becomes large in proportion to changes in the load applied to the disk, and the pressure range of the disk which may be adapted for the kind of slurry is also very large.